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* Wireguard: bump tag to most recent since it breaks building on 5.4.y * Move rockchip current to 5.4.y * Move sunxi current to 5.4.y * Move meson64 to 5.4.y * Move odroidxu4 to 5.4.y and enable "current" targets * Enable missing target
71 lines
2.8 KiB
Diff
71 lines
2.8 KiB
Diff
From patchwork Wed Oct 2 19:44:06 2019
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Content-Type: text/plain; charset="utf-8"
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MIME-Version: 1.0
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Content-Transfer-Encoding: 7bit
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Subject: [v2] drm/bridge: dw-hdmi: Refuse DDC/CI transfers on the internal I2C controller
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From: Matthias Kaehlcke <mka@chromium.org>
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X-Patchwork-Id: 334046
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Message-Id: <20191002124354.v2.1.I709dfec496f5f0b44a7b61dcd4937924da8d8382@changeid>
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To: Archit Taneja <architt@codeaurora.org>, Andrzej Hajda <a.hajda@samsung.com>,
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Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
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David Airlie <airlied@linux.ie>
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Cc: Jernej Skrabec <jernej.skrabec@siol.net>,
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Tzung-Bi Shih <tzungbi@chromium.org>,
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Neil Armstrong <narmstrong@baylibre.com>,
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Sean Paul <sean@poorly.run>, Douglas Anderson <dianders@chromium.org>,
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dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
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Matthias Kaehlcke <mka@chromium.org>, Cheng-Yi Chiang <cychiang@chromium.org>,
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Yakir Yang <kuankuan.y@gmail.com>, Jerome Brunet <jbrunet@baylibre.com>
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Date: Wed, 2 Oct 2019 12:44:06 -0700
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The DDC/CI protocol involves sending a multi-byte request to the
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display via I2C, which is typically followed by a multi-byte
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response. The internal I2C controller only allows single byte
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reads/writes or reads of 8 sequential bytes, hence DDC/CI is not
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supported when the internal I2C controller is used. The I2C
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transfers complete without errors, however the data in the response
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is garbage. Abort transfers to/from slave address 0x37 (DDC) with
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-EOPNOTSUPP, to make it evident that the communication is failing.
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Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
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Reviewed-by: Douglas Anderson <dianders@chromium.org>
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Reviewed-by: Sean Paul <sean@poorly.run>
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Acked-by: Neil Armstrong <narmstrong@baylibre.com>
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---
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Sorry for the delay with sending v2, I completely forgot about this patch ...
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Changes in v2:
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- updated comment with 'TOFIX' entry as requested by Neil
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- added Neil's 'Acked-by' tag
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drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 10 ++++++++++
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1 file changed, 10 insertions(+)
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diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
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index 52d220a70362..ac24bceaf415 100644
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--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
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+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
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@@ -41,6 +41,7 @@
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#include <media/cec-notifier.h>
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+#define DDC_CI_ADDR 0x37
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#define DDC_SEGMENT_ADDR 0x30
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#define HDMI_EDID_LEN 512
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@@ -439,6 +440,15 @@ static int dw_hdmi_i2c_xfer(struct i2c_adapter *adap,
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u8 addr = msgs[0].addr;
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int i, ret = 0;
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+ if (addr == DDC_CI_ADDR)
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+ /*
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+ * The internal I2C controller does not support the multi-byte
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+ * read and write operations needed for DDC/CI.
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+ * TOFIX: Blacklist the DDC/CI address until we filter out
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+ * unsupported I2C operations.
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+ */
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+ return -EOPNOTSUPP;
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+
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dev_dbg(hdmi->dev, "xfer: num: %d, addr: %#x\n", num, addr);
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for (i = 0; i < num; i++) {
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